1. Technical Field of the Invention
The present invention relates to a method for manufacturing a metal-insulator-metal (MIM) capacitor; more particularly, a method for manufacturing a MIM capacitor having a bottom electrode including copper, which can effectively prevent the lifting of thin films and the oxidation of the bottom electrode.
2. Discussion of the Related Art
As semiconductor devices become more highly integrated and the usage of the semiconductor devices in electronic devices, such as information processing apparatuses and home appliances, increases, the semiconductor devices are required to have a larger processing capacity and faster processing speed.
In general, the storage capacity of a random access memory (RAM) chip can be expressed empirically by using Moore"" law indicating the general development of a memory chip. According to Moore"" law, the storage capacity of a memory chip increases four times every three years. The increase of the storage capacity of a memory chip is accomplished by reducing the size of the semiconductor device, and increasing the length of a silicon chip in accordance with the size reduction of the semiconductor device.
As the size of the semiconductor device installed in the silicon chip is reduced, interconnect lines of the semiconductor device are also reduced. The reduction in the size of a semiconductor device also causes the interconnect lines to be disposed closer together. When the interconnection lines are closely disposed, the interconnect lines interfere with each other. If the interval between the interconnection lines falls below a predetermined value, the entire signal is delay because of the interference between the interconnection lines. To increase the processing speed of a semiconductor device, a reduction of the specific resistance in the metal used for forming the interconnection lines is required.
Typically, the interconnection lines of a semiconductor device are formed using aluminum (Al) or aluminum alloy having the specific resistance of approximately 2.66 xcexcxcexa9 cm. In 1998, International Business Machine Co. disclosed a method for forming interconnection lines with copper (Cu). Various researchers have been developing methods for forming and improving the formation of interconnection lines, e.g., a metal wiring or a metal-insulator-metal (MIM) capacitor using copper.
Other methods of forming a semiconductor device using copper are disclosed in U.S. Pat. No. 5,935,762 (issued to Chang-Ming Dai), Korean Laid Open Patent Publication No. 2001-110919, and Korean Laid Open Patent Publication No. 2002-55887.
In addition, Japanese Laid Open Patent Publication No. 2000-352827 provides a method for removing a hardened photoresist generated during the patterning of an insulation film using a non-oxidation gas after the insulation film is formed on a metal film including copper. Also, Japanese Laid Open Patent Publication No. 2000-82695 discloses a method for removing a copper halide based compound formed during the etching of a copper thin film with a halogen gas like chlorine (Cl2) after forming a passivation film including titanium (Ti), titanium compound, tantalum compound, tungsten compound or aluminum alloy on the copper thin film.
FIGS. 1A to 1C are cross-sectional views illustrating a conventional method of manufacturing a metal-insulator-metal capacitor including a copper bottom electrode.
Referring to FIG. 1A, after an interlayer dielectric film 15 including oxide is formed on a semiconductor substrate 10 such as a silicon wafer, the interlayer dielectric film 15 is etched to form a groove or a trench in the interlayer dielectric film 15.
With a copper damascene process, a copper film is deposited in the trench or the groove by a sputtering process, a chemical vapor deposition process, or an electro plating process. Then, the copper film is polished using a chemical-mechanical polishing (CMP) process, thereby forming a metal wire 20 in the interlayer dielectric film 15.
Subsequently, a dielectric film 25 is formed on the interlayer dielectric film 15 including the copper metal wire 20, and a top electrode film 30 is formed on the dielectric film 25. The top electrode film 30 includes tantalum (Ta), tantalum nitride (TaN), titanium (Ti), or titanium nitride (TiN).
Referring to FIG. 1B, to manufacture the MIM capacitor, a photoresist film is coated on the top electrode film 30, and the photoresist film is patterned so that a photoresist pattern 35 is created for forming a top electrode of the MIM capacitor.
Referring to FIG. 1C, the top electrode film 30 is etched using the photoresist pattern 35 as an etching mask such that the top electrode 40 is formed on the dielectric film 25.
When the photoresist pattern 35 is removed using an ashing process and a rinsing process, the MIM capacitor 50 having the copper bottom electrode is formed on the substrate 10.
In a conventional method for manufacturing the MIM capacitor, a hard metallic polymer is formed when the top electrode film having a thickness of below 1,000 xc3x85 is etched, forming the top electrode. The hard metallic polymer includes metal oxide or metal nitride like tantalum oxide (TaOx), tantalum nitride (TaNx), titanium oxide (TiOx), titanium nitride (TiNx) or carbon nitride (CNx) wherein x denotes a positive number. It is difficult, if not impossible, to remove the hard metallic polymer by using an ashing process or a wet cleaning process.
FIGS. 2A and 2B are cross-sectional views showing the disadvantages of the conventional method for manufacturing the MIM capacitor.
Referring to FIGS. 1B and 2A, when the top electrode film 30 is etched using the photoresist pattern 35 as the etching mask, the metal or the metal compound of the top electrode film 30 such as tantalum, tantalum nitride, titanium, or titanium nitride can be reacted with an etching gas including chlorine (Cl2), nitrogen (N2) and boron chloride (BCl3). As a result, the hard metallic polymer 55 including metal oxide or metal nitride adheres to the side of the photoresist pattern 35.
Because the hard metallic polymer 55 cannot be removed using the ashing or the wet cleaning process, the hard metallic polymer 55 remains on the top electrode 40 of the MIM capacitor 50 even after the photoresist pattern 35 is removed. While performing a successive process, the hard metallic polymer 55 remains and a metal wiring is formed on the MIM capacitor 50 and electrically connects the top electrode 40 of the MIM capacitor 50. Thus, an electrical short is formed between the MIM capacitor 50 and the metal wiring.
The hard metallic polymer 55 can be removed using a high temperature ashing process that uses an O2 gas and a CF4 gas at a high temperature, e.g., above 250xc2x0 C. As shown in FIG. 2, the thin films of the MIM capacitor 50 like the bottom electrode, the dielectric film, and the top electrode may be lifted because of the different thermal characteristics, e.g., coefficient of thermal expansion, of each of the thin films influenced by the high temperature associated with the ashing process. In particular, the top electrode and the dielectric film may be lifted during the high temperature ashing process.
In addition, the copper bottom electrode and other metal film may be easily oxidized during the high temperature ashing process, which creates a MIM capacitor having a uniform capacitance or the capacitance of the MIM capacitor may not meet a desired value. Thus, the overall failure rate of the capacitor may be high during the manufacturing process. Those failures may relate to the thermal characteristics of the thin films of the MIM capacitor, and to the structural characteristic of the MIM capacitor including the thin films having a thickness of below 1,000 xc3x85.
A need therefore exists for a method of manufacturing a metal-insulator-metal (MIM) capacitor which prevents oxidizing of a bottom electrode and lifting of thin films of the MIM capacitor by effectively removing a hard metallic polymer formed during the formation of the MIM capacitor
According to an embodiment of the present invention, a method is provided for manufacturing a metal-insulator-metal capacitor by employing a dual damascene process, which can efficiently remove a hard metallic polymer with an etching gas at a predetermined temperature.
According to another embodiment of the present invention, a method is provided for manufacturing a metal-insulator-metal capacitor by forming a metal wire including copper on a substrate, after the metal wire including copper is formed on the substrate, a dielectric film is formed on the metal wire. Then, a top electrode film, e.g., tantalum, tantalum nitride, titanium, titanium nitride, ruthenium, or platinum, is formed on the dielectric film, and etched to form a top electrode. Subsequently, a hard metallic polymer, e.g., tantalum oxide, tantalum nitride, titanium oxide, or titanium nitride, is formed during the etching process to etch the top electrode film using a gas mixture including an oxygen gas and a fluorocarbon based gas such as CF4, C2F6, C3F8, C4F6, or C5F8 at a temperature in the range of about 150xc2x0 C. to about 250xc2x0 C. for approximately 20 to 40 seconds. The flow rate of the fluorocarbon based gas is about 2 percent or less of the flow rate of the gas mixture.
According to another embodiment of the present invention, a method is provided for manufacturing a metal-insulator-metal capacitor by employing a dual damascene process. The method provides forming an insulation film on a semiconductor substrate, and forming a via hole and a trench in the insulation film. Next, a contact including copper and a metal wiring including copper are formed in the via hole and in the trench, respectively. After the formation of the contact and the metal wiring, a dielectric film is formed on the insulation film and the metal wiring. Next, a top electrode film is deposited on the dielectric film. Then, the top electrode film is coated with a photoresist, and the photoresist is patterned to form a top electrode of the MIM capacitor. Next, the top electrode film is etched to form the top electrode. A hard metallic polymer is formed during the etching process, which removes the top electrode film from the top electrode.
According to the embodiments of present invention, the hard metallic polymer formed during the formation of the top electrode of the MIM capacitor can be removed using a gas mixture including an oxygen gas and a fluorocarbon based gas at a predetermined temperature. The predetermined temperature is based in part on the thermal characteristics of the thin films like the top electrode, the dielectric film, and the bottom electrode. Therefore, the lifting of the thin films can be effectively prevented, and the yield of the manufacturing process for manufacturing the MIM capacitor can be significantly increased. Also, the MIM capacitor has a uniform capacitance because the damage to the dielectric film is prevented, and the oxidation of the bottom electrode is prevented.